In a series of tweets, Mr. Trump asserted that he has “complete pardon power,” although he did not say he intended to exercise that power immediately.  These remarks, combined with earlier reports that he has been consulting legal counsel about the extent of his power to pardon, certainly raise the prospect that he may seek to block the progress of the Mueller investigation by prospectively pardoning those who are its subjects, possibly including himself.

Should he do so, several issues alluded to previously here and in my recent Slate article will jump to the forefront: (1) whether a president can issue prospective pardons, i.e., can he pardon people for crimes with which they have not yet been charged; (2) whether a president can pardon himself; and (3) whether the use of the pardon power to block an investigation into wrongdoing by the president or his close associates would itself constitute either the crime of obstruction of justice or an impeachable offense.

The answer to the first question is probably yes.  At a minimum, we have the historical example of President Gerald Ford who pardoned his predecessor, the recently-resigned Richard Nixon, for criminal offenses he might have committed in connection with the Watergate scandal.

Whether a president can pardon himself is hotly contested, but if he can, the constitution expressly provides that such a pardon cannot extend to impeachment.

Whether an exercise of the pardon power to block an investigation could itself constitute a crime is a fascinating, but unresolved, question.  My own instinct is that it could be.  Merely because a government officer has the legal power to perform an act does not mean that the act is not criminal.  For example, a member of Congress has the undoubted power to vote for or against legislation, but if the member votes a particular way because she received a bribe to do so, that would be a crime.  Presidents are no different.

Finally, I find it almost inarguable that a corrupt exercise of the pardon power would constitute grounds for impeachment.  On this blog, we have not yet discussed what kinds of conduct can constitute an impeachable offense.  However, the undisputed core of impeachable behavior is misuse of presidential power.  The fact that the power in question is that of issuing pardons does not change this fundamental conclusion.

All these questions will be discussed on this site in greater detail presently.  In the meantime, I strongly recommend a fine new law review article by Professors Daniel Hemel and Eric Posner on presidential obstruction that covers in detail or touches on all of them. It can be downloaded at this link.